The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The present invention generally relates to a handguard system for a rifle.
Semi-automatic rifles are some of the most popular sporting firearms in the world. These rifles rely on gas-operated reloading for automatic operation. In the firing cycle of semi-automatic rifles, a portion of combustion gas that propels a bullet from the rifle is used to operate a bolt mechanism at the receiver to reload another cartridge into the rifle chamber for subsequent firing. Since the gas is primarily used to propel the bullet through the barrel, relatively low-pressure gas is typically vented through the reloading system from at or near the muzzle. This requires some form of piston chamber or tube to communicate this gas from the muzzle backwards to the receiver. Among the types of mechanisms to effect automatic reloading are piston and direct impingement systems. In a piston-driven system, the piston is mechanically fixed to the bolt group and moves through the entire operating cycle. A direct impingement system eliminates the piston by venting combustion gas through a tube from the muzzle to the receiver of the rifle where gas forces components to directly impinge on the bolt carrier.
With either system, the user typically supports the rifle by holding a handguard that surrounds the barrel and the portions of the gas system that are forward of the receiver. On “AR” type rifles with free-floating barrels, the handguard is affixed to a barrel nut. The barrel nut also secures the barrel to the upper receiver. Barrel nuts must also be configured to allow the gas system components to communicate energy (in a piston system) or combustion gas (in a direct impingement system) into the receiver. To accommodate both the gas system and handguard, typical barrel nuts will have multiple, radially-spaced holes or sprocket-like notches to allow the gas tube or piston component to pass over or through the nut and into the receiver. To affix the handguard to the nut, some handguards will utilize the barrel nut notches with a spring-tensioned ring or be secured by bolts through the handguard into the nut via a series of tapped holes in the nut.
With either method of affixing both the barrel and handguard to the receiver, the barrel nut must be “timed” to exactly align one or more of the gas component holes and the handguard-securing holes. Such alignment ensures the gas system components are not improperly stressed or bent during function and that front sights or other precise components attached to the handguard are positioned in a desired manner.
Timing the barrel nut for proper alignment of the gas system, receiver, and handguard can be troublesome and time consuming. And since the barrel nut must be secured within certain torque tolerances, alignment may become even more complicated. Typically, one or more shims may be placed between the nut and receiver to achieve proper torque and alignment. However, shim placement is often time consuming as proper alignment can only be measured when a shim is in place. If the placed shim does not achieve the desired results, the process must be repeated until alignment within torque tolerances is achieved.